Oil gauge

ABSTRACT

A method of and apparatus for checking the liquid level in a container according to which a tubular member is immersed into said liquid and below its minimum level, whereupon liquid and air is trapped in said tubular member by a piston and a seal about the rod of a piston and the air is compressed by the entrapped liquid, the compression stroke on the entrapped liquid and air furnishing an indication for the liquid level in the respective container.

O6-U-72 OR 396671295 United States Patent [151 3,667,295

Skutella [4 1 June 6, 1972 54] OIL GAUGE 1,526,376 2/1925 Rosenmund..73/290 R Inventor: Stanislaus skuteua, Rothweg 6 A, 791 1 2,057,03410/1936 Kinney ..73/290 R Pfaffenhofen-Roth, Germany FOREIGN PATENTS ORAPPLICATIONS Filed? P 2, 1970 853,853 12/1939 France ..73/290 R [2]]App]. No: 68 932 1,189,271 10/1959 France ..73/290 R PrimaryExaminer-Louis R. Prince [30] Foreign Application Priority DataAssistant ExaminerDenis E. Corr Attorney-Wa1ter Becker Sept. 6, 1969Germany ..P 19 45 241.6

, [57] ABSTRACT [52] U.S. Cl. ..73/290 R 51 1.... c1. ..G01f 23/00 Amethod of and apparatus for checking the liquid level in a {53] Field 0'Search 73/290 R, 290 1 16/] 109 container according to which a tubularmember is immersed into said liquid and below its minimum level,whereupon [56] Reierences Cited liquid and air is trapped in saidtubular member by a piston and a seal about the rod of a piston and theair is compressed UNITED STATES PATENTS by the entrapped liquid, thecompression stroke on the entrapped liquid and air furnishing anindication for the liquid 2,539,604 l/ l 951 Woolley ..73/290 R level inthe respective cmainer 1,526,377 2/1925 Rosenmund ..73/290 R 1,521,19512/1924 Johnson ..73/290 R 11 Claims, 5 Drawing Figures PATENTEDJuu 6I972 sum 10F 3 IN VEN TOR 900/3/005 SIu/e/h OIL GAUGE The'presentinvention relates to a method of and device for checking the liquidlevel in a container, especially the oil level in the crankcase of apiston engine, by means of a cylinder communicating with the containerwhile in the cylinder a piston is displaceable in conformity with therespective liquid level, and the stroke of the piston can be read.

Devices of this type which preferably serve for checking the oil levelin vehicle-internal combustion engines, have become known. According tosuch devices, the piston is displaced from an upper starting position indownward direction up to the oil level after the cylinder at the startof the piston movement has been closed at the bottom by a valve or anextension of the piston which extension forms a control valve. Duringthe measuring stroke, the air entrapped above the oil level escapesthrough an opening in the piston which, when the piston engages the oillevel, is closed by a valve.

According to other heretofore known devices, the opening in the pistonforms a throttling area of such small cross-section that, after the airduring the downward stroke of the piston has escaped, the considerablyhigherflow resistance of the succeeding lubricating oil gives anindication of the respective height of the oil level. The closing of thecylinder and of the piston opening by valves and also the design in theform of a throttling area have inherent a certain lack of precision inthe gauging in view of the fact that the area of the valve closure andthe increase in pressure will in case of the throttling area depend onthe speed of the piston movement. A soiling or hardening of the oil,especially at those areas which are above the oil level, can easilyimpair the functioning of the device.

Inasmuch as the reliability of the gauging is of extreme importance forthe engine, it is an object of the present invention to provide an oilgauge which will overcome the above mentioned drawbacks.

This object and other objects and advantages of the invention willappear more clearly from the following specification in connection withthe accompanying drawings, in which:

FIG. 1 illustrates a gauge which comprises a piston operable by a Bowdenwire and adapted to be displaced in upward direction for carrying out ameasuring strok FIG. 2 shows a device similar to that of FIG. 1 but withthe measuring stroke of the piston effected in downward direction bymeans of a cable or the like.

7 FIG. 3 illustrates a gauge according to the invention which isoperable manually by direct engagement of the piston rod.

FIG. 4 shows a device according to the invention with remote control byan electric motor.

FIG. 5 illustrates a gauge according to the invention in which themeasuring operation is effected by means of a pressure fluid cylindermounted above the measuring cylinder.

The method according to the invention for checking the liquid level of afluid is characterized primarily in that the cylinder is at the start ofthe piston movement closed at the bottom and at the top so that the airabove the liquid level remains entrapped during the subsequent pistonstroke in the cylinder. The closing of the cylinder at the bottom and atthe top at the start of the piston movement can easily be controlled sothat the reliability of the measuring step is not affected orendangered. On the other hand, tests have proved that the elasticity ofthe air entrapped in the cylinder during the measuring stroke does notendanger the usefulness of the measuring operation. In this connectionit should be noted that on one hand the checking of the liquid level isnot intended to represent an absolute measurement, but, especially whenthe oil level in the crankcase of an internal combustion.

engine is involved, it is merely intended to ascertain whetherandapproximately where the liquid level is located within the prescribedlimits. On the other hand, even when carrying out the measuring strokemanually, only negligible differences in the measured results willoccur. The compression pressure will during the stroke increaseprogressively to such an extend that a stroke limitation can easily befelt. Deviations in the measurement may furthermore be reduced bycarrying out the measuring stroke by means of a small handle to whichcan be applied manual forces only not forces exerted by the arm.

With respect to a device for carrying out the method according to theinvention, it is suggested that the piston is displaceable from astarting position below the lowermost liquid level in upward directionwhile it will first close the lower cylinder opening. This direction ofthe piston stroke primarily has the advantage that the measuring strokeis carried out by direct engagement of a pulling member, for instance aBowden wire, with the piston rod which pulling member may, for instance,extend from the crank housing of the motor to the dashboard of thevehicle where the actuation of said member is effected.

A further advantage of the stated stroke direction consists in that thepiston when occupying its starting position, is located below the liquidlevel so that the seals will not stick. The above mentioned advantagesalso apply when the air above the liquid level does not remain entrappedin the cylinder during the measuring stroke.

Furthermore, in the device according to the present invention the pistonrod which extends from the cylinder at the upper end thereof isadvantageously designed in the form of a slide which closes aguiding'bore at the start of the piston stroke. Such positive controlwhich is directly related to the movement of the piston will, similar tothe movement of the piston, result in a maximum degree of reliability.

A device according to the invention for checking the liquid level mayinversely also be so designed that the piston is from its startingposition displaceable in downward direction while a piston rod acting ascontrol slide or valve spool will at the start of the piston strokeclose a previously open guiding bore at the lower end of the cylinder.If the measuring stroke is effected by means of a pulling member, alever or roller reversing the direction of movement of the lever may beinterposed.

The piston is advantageously sealed by means of a simple 0- ring or byanother equivalent soft seal in the cylinder. For the purpose involvedin the present case, it may under certain circumstances suffice toprovide a close fit between the piston and the cylinder without anadditional seal. Similar remarks apply to the piston rod acting as slideor valve spool. The piston rod may be provided with a seal in the formof an O-ring or may be sealed solely by a suitable fit of the piston rodand the guiding bore.

The device according to the invention for checking the liquid level may,in a manner known per se, be actuated by directly manually engaging thepiston rod or may be remote controlled. The oil level in a motor locatedin front of a vehicle is advantageously checked by hand by means of apulling member provided at the dashboard. When longer distances areinvolved, for instance between the motor located in the rear of a busand the dashboard, also an actuation by means of an electric motor or apressure fluid motor may be effected. The measured result may also beindicated at the dashboard by means of an electric device.

Referring now to the drawings in detail and FIG. 1 thereof inparticular, the cylinder 1 shown therein is connected by a flange 2 inthe opening of the crankcase of the internal combustion engine in such away that the lower end of the cylinder is immersed below the lowermostoil level. In the illustrated lower starting position, the piston 3 islocated closely below the lower edge of the cylinder so that a freeconnection with the crank chamber or crank pit is established. Thepiston rod 4 is guided in a reduced upper portion 5 of the cylinder. Along groove 6 in the upper portion of the piston rod establishescommunication between the air chamber 7 of the cylinder 1 above the oillevel with the air chamber of the crank housing. Cylinder and crankhousing thus communicate freely with each other which means the oillevel will have the same height in the crank housing and said cylinder.

The piston 3 and the piston rod 4 each comprise an O-ring 8, 9 forsealing the cylinder 1 or for establishing a seal in the upper portion 5serving as guiding means. Inasmuch as wear is hardly to be expected, itwill be appreciated that, depending on the material and tolerance of thefitting, a separate seal may not be needed.

A Bowden wire fastened to piston rod 4 extends to the dashboard of themotor vehicle where the steel wire is connected to the circumference ofa pulley 11. A handle 12 connected to the pulley 11 or its shaft andsimultaneously serving as pointer also serves for actuating themeasuring stroke. A helical spring 13 returns the piston to its startingposition. Shortly after the measuring stroke has started, the cylinderis closed at the bottom and at the top, and the entrapped oil is liftedby the piston until the air entrapped thereabove has been compressed tosuch an extent that at the end position of the piston, the air acts likea fixed abutment. Preferably, the interior of the reduced portion 5 isin communication with a pressure gauge G which indicates the compressionof the compressed air above the piston rod 4. While the stroke of pistonrod 4 may be read in any convenient manner, e.g. through a sight glassin part 5, gauge G may instead be provided with an additional sealindicating the respective stroke of piston rod 4 corresponding to therespective desired pressure to which the air above piston rod 4 is to becompressed for each liquid level measurement.

With the device illustrated in FIG. 2, the measuring stroke of thepiston 3 is carried out in a downward direction. In the illustratedupper starting position, the piston frees the connecting openings 15 tothe space above the oil level. A lower extension 16 of the piston rod 17acts as slide or valve spool which, after a short starting stroke,immerses in guiding means 18 at the lower cylinder end whereby thecylinder is closed. The measuring stroke of the piston is effected by acable 19 which engages the upper end of the piston rod and is deviatedby a roller 20. A spring 21 for returning the piston to its startingposition will in this design be located within the measuring cylinder.

The device according to FIG. 3 fundamentally corresponds to the deviceof FIG. 1 and excels by a great simplicity. More specifically, thepiston rod 24 of piston 25 is at its upper extension 26 provided with aneye 27 for a direct manual actuation. The extension '26 has a somewhatshorter diameter than the piston rod 24 so that in the starting positionof the measuring stroke an air connection is established through anannular gap. The closure is effected by the piston simultaneously withthe closure of the'lower end of the cylinder. Inasmuch as the eye 27permits an actuation in both directions, a spring for the return strokebecomes superfluousj'For purposes of indicating the measuring result, ascale is provided on the extension 26 of the piston rod.

The remote controlled device according to the invention of FIG. 4employs an electric motor 30 with stepdown transmission and a crank pin31 which through-the intervention of a pushrod 32 and a strokecompensating spring 33 engages the upper end of the piston rod 34 andcarries out the measuring stroke of the piston 35 over half arevolution. Following the engagement of the motor, the latter will runup to the oppositely located dead center position of the crank pin 31 atwhich non-illustrated limit switches interrupt the current. When themotor is again turned on, the crank pin 31 returns to the illustratedstarting position while the piston is by a spring 36 likewise returnedto its starting position. A contact 37 of a sliding resistor 38 whichcontact is insulated and arranged at the upper end of the piston rod 34,indicates the respective piston stroke on an electric measuring device39 which can be viewed by the driver.

Finally, FIG. 5 illustrates a device which is likewise remotecontrolled. Coaxial above the measuring cylinder 40 there is provided apressurefluid cylinder 41 the piston 42 of which is provided on theextended measuring piston rod 43. A magnetic valve 44 operable from thedriver's seat establishes communication between a non-illustratedpressure fluid container and the cylinder through a conduit 45 forbringing about the measuring stroke. A slide or valve spool 46 providedon the valve shank blocks the connection with a relief opening 47thereabove through which, following the completion of the measuringoperation and after again closing the valve, the compressed air escapesfrom the cylinder 41 into the atmosphere. An electric indication visibleby the driver is brought about by the same means as described inconnection with the device of FIG. 4.

Devices of the type set forth above in connection with FIGS. 4 and 5 areintended primarily for longer distances, as for instance between thedriver's seat and the driving engine in the rear end of a bus.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular showing in the drawings but alsocomprises any modifications within the scope of the appended claims.

What I claim is:

l. A method of checking the liquid level in a container, especially theoil level in a crank case of a reciprocable piston engine, whichincludes the steps of: immersing a tubular member into the liquid thelevel of which is to be measured and below the minimum level of saidliquid so that the liquid level in said tubular member will be thesameas in the container, entrapping the thus obtained liquid column in saidtubular member and the air above said liquid column while compressingsaid air by said liquid column until a predetermined resistance isencountered, and measuring the stroke of said liquid column necessary toobtain said predetermined resistance.

2. An' apparatus for checking the liquid level in a container,especially the oil level in a crank case of a reciprocable pistonengine, which includes cylinder means open at one end, said end beingimmersable into and below the minimum liquid level in a container,control means selectively reciprocable in :said cylinder means from afirst position in which air and liquid can pass into and out of saidcylinder means to a selected second position in which the liquid and airin said cylinder means are entrapped and said last mentioned air will becompressed by said control means, and means for measuring the respectivecompression stroke of said control means.

3. An apparatus according to claim 2, in which said cylinder meanscomprises a lower larger diameter section to be immersed in the liquidthe level of which is to be measured and also comprises an upper smallerdiameter section, and in which said control means includes a pistonmovable from a position outside and below said larger diameter sectioninto said larger diameter section so as to sealingly engage the same,said control means also including a piston rod connected to said pistonand movable into said upper smaller diameter section so as to sealinglyengage the same.

4. An apparatus according to'claim 3, in which said piston is providedwith a sealing O-ring engaging said cylinder means.

5. An apparatus according to claim 3, in which said piston rod isprovided with a sealing O-ring engaging said cylinder means.

6. An apparatus according to claim 2, in which said cylinder meanscomprises a lower narrower diameter section to be immersed into theliquid the level of which is to be measured and also comprises an upperlarger diameter section, and in which said control means includes apiston sealingly reciprocable in said upper section and also includes apiston rod connected to said piston and movable selectively from saidupper section into said lower section to sealingly engage the same andentrap liquid and air in said upper section and compress the airtherein.

7. An apparatus according to claim 6, in which said piston is providedwith a sealing O-ring engaging said cylinder means.

8. An apparatus according to claim 4, in which said piston rod isprovided with a sealing O-ring engaging said cylinder means.

9. An apparatus according to claim 2, which includes spring meansassociated with said control means and continuously urging said controlmeans to said first position.

10. An apparatus according to claim 2, which includes electric motormeans with stepdown transmission means and pressure operable pistonmeans operatively connected to said control means for actuating thelatter to bring about a liquid level measuring operation, and remotecontrollable valve means operatively connected to said fluid operablepiston means for controlling the supply of actuating fluid to and fromsaid last mentioned piston means.

a n a n 1-

1. A method of checking the liquid level in a container, especially theoil level in a crank case of a reciprocable piston engine, whichincludes the steps of: immersing a tubular member into the liquid thelevel of which is to be measured and below the minimum level of saidliquid so that the liquid level in said tubular member will be the sameas in the container, entrapping the thus obtained liquid column in saidtubular member and the air above said liquid column while compressingsaid air by said liquid column until a predetermined resistance isencountered, and measuring the stroke of said liquid column necessary toobtain said predetermined resistance.
 2. An apparatus for checking theliquid level in a container, especially the oil level in a crank case ofa reciprocable piston engine, which includes cylinder means open at oneend, said end being immersable into and below the minimum liquid levelin a container, control means selectively reciprocable in said cylindermeans from a first position in which air and liquid can pass into andout of said cylinder means to a selected second position in which theliquid and air in said cylinder means are entrapped and said lastmentioned air will be compressed by said control means, and means formeasuring the respective compression stroke of said control means.
 3. Anapparatus according to claim 2, in which said cylinder means comprises alower larger diameter section to be immersed in the liquid the level ofwhich is to be measured and also comprises an upper smaller diametersection, and in which said control means includes a piston movable froma position outside and below said larger diameter section into saidlarger diameter section so as to sealingly engage the same, said controlmeans also including a piston rod connected to said piston and movableinto said upper smaller diameter section so as to sealingly engage thesame.
 4. An apparatus according to claim 3, in which said piston isprovided with a sealing O-ring engaging said cylinder means.
 5. Anapparatus according to claim 3, in which said piston rod is providedwith a sealing O-ring engaging said cylinder means.
 6. An apparatusaccording to claim 2, in which said cylinder means comprises a lowernarrower diameter section to be immersed into the liquid the level ofwhich is to be measured and also comprises an upper larger diametersection, and in which said control means includes a piston sealinglyreciprocable in said upper section and also includes a piston rodconnected to said piston and movable selectively from said upper sectioninto said lower section to sealingly engage the same and entrap liquidand air in said upper section and compress the air therein.
 7. Anapparatus according to claim 6, in which said piston is provided with asealing O-ring engaging said cylinder means.
 8. An apparatus accordingto claim 4, in which said piston rod is provided with a sealing O-ringengaging said cylinder means.
 9. An apparatus according to claim 2,which includes spring means associated with said control means andcontinuously urging said control means to said first position.
 10. Anapparatus according to claim 2, which includes electric motor means withstepdown transmission means and crank pin means operatively connected tosaid control means, and limit switch means operatively connected to saidelectric motor means and said crank pin means and operable in responseto one-half revolution of said crank pin and the completion of acorresponding measuring stroke of said control means to break thecircuit for said electric motor means.
 11. An apparatus according toclaim 2, which includes fluid pressure operable piston means operativelyconnected to said control means for actuating the latter to bring abouta liquid level measuring operation, and remote controllable valve meansoperatively connected to said fluid operable piston means forcontrolling the supply of actuating fluid to and from said lastmentioned piston means.